var xxx = ".gif";
var da = 3;
var alph=100;
var obj = document.getElementById('photo');

function fadeIn(){
alph += da;
obj.style.filter = "alpha(opacity="+alph+")";
obj.style.opacity = 1-alph / 100;
obj.style.MozOpacity = alph / 100;
obj.style.KhtmlOpacity = alph / 100;
if (alph < 100) {setTimeout("fadeIn()",1)};
}

function photoOver(n){
alph = 1;
obj.style.filter = "alpha(opacity="+alph+")";
obj.src = pth+"images/photo"+n+xxx;
fadeIn();
}